1. Field of the Invention
The present invention relates generally to devices and methods for covering open top rail cars and, more specifically, to such devices and methods for covering open top coal cars transporting coal.
2. Description of the Prior Art
There are a number of rail lines in use at the present time in the United States for conveying coal from mines to other locations of use, such as a power plant. The accumulation of ballast/coal dust mixtures along the tracks can cause the installation to retain water, lose compressive strength and ultimately cause track surface irregularities. These problems are in addition to the obvious environmental impact.
There are presently three basic types of coal cars in use in the United States. They are all “open top” cars. The first of these is the bottom dump hopper car. Early bottom dump railcars utilized manual discharge gates which had to be opened and closed individually by hand. This made unloading slow and expensive. However, beginning in the late 1970s, fully automated bottom dump cars came into widespread use. Fully automated bottom dumpers use onboard compressed air to pneumatically open and close the discharge gates upon receipt of an appropriate electrical signal. This allows bottom dump trains to unload while moving.
The second type car in frequent use is the rotary dump gondola. The development of the high capacity rotary dump gondola in the early 1970s led to huge efficiency gains in coal transportation compared to traditional manually-operated bottom-dump hopper cars. Rotary dump cars are less expensive to manufacture and maintain since they have no moving parts other than the wheelsets, couplers, and brake rigging. They are generally lighter than bottom dump hoppers, which means increased coal capacity.
The most versatile coal cars in operation are the third type of cars known as combination hoppers, or simply as “combo-cars.” They can be used in bottom dump or rotary dump operations. This style of cars is popular with large utilities who pool cars between multiple power plants thus requiring the car fleet to be capable of either bottom dump or rotary dump operation.
No matter which of the three basic car types is utilized, the open top of the car allows a certain amount of coal dust to blow out on the trip from the mine to the power plant or other distant location. Because a number of operational and environmental problems are associated with this unwanted discharge, various types of coal car “covers” have been proposed. The following patents are illustrative of the general state of the prior art.
U.S. Pat. No. 7,823,515, issued Nov. 2, 2010, to Schaefer et al., shows a rail car cover system including a rail car, a first cover section and a second cover section. The first cover section includes a first hinge mechanism and a first cover material. The second cover section includes a second hinge mechanism and a second cover material. The first cover section and the second cover section are both movable between a closed configuration and an open configuration. When in the closed configuration, the first cover section and the second cover section substantially cover the opening in the top of the rail car.
U.S. Pat. No. 7,594,474, issued Sep. 29, 2009, to Zupancich, shows an open-top rail car cover which is defined by a frame having dimensions sufficient to fit an open-top freight car. A latch disposed about a side of the frame includes a first flange and a second flange that combine to define a means for receiving an engagement member of a rail car. Both the first and second flanges include at least one first aperture and at least one second aperture designed to receive a means for securing the car cover to the rail car. The first and second apertures have dimensions sufficient to permit movement of the first and second flanges.
U.S. Pat. No. 7,083,375, issued Aug. 1, 2006, to Lewis et al., describes a system and method for handling and transporting moist bulk grain by-products by means of a rail car having an aluminum car body carried by a plurality of trucks for engaging rails. A flexible top cover, supported by a plurality of breakaway curved ribs, is positioned over an open top of the rail car to protect the moist bulk grain by-products carried therein. The car body has a front end and a rear end each having a wind screen for spoiling or deflecting the flow of air over the car as it moves to prevent the flexible top cover from being lost or damaged.
U.S. Pat. No. 6,250,233, issued Jun. 26, 2001, to Luckring, shows an extendable and retractable cover for use on gondola railroad cars, preferably provided as a kit for retrofitting existing cars. The kit includes a series of elongated runners for attaching to the top of longitudinal walls of the gondola railroad cars, the runners including at least one slidable surface, for supporting and permitting transport over the surface of a plurality of tarp supports, which extend across the lateral opening between the sidewalls of the gondola railroad car. The supports are configured to slide over the runners while enclosing an edge of the runner so as to engage the runner and retain the vertical position and orientation of the supports during transposition across the surface of the runners. The tarp support members support a flexible sheet tarpaulin, impermeable to rain and the elements, above the tarp supports.
U.S. Pat. No. 4,368,674, issued Jan. 18, 1983, to Wiens et al., describes a hatch cover for railroad hopper cars and a method of constructing same. The hatch cover includes a main panel and a stepped periphery, both of which are constructed of polyester resin impregnated with glass fiber reinforcement. Stiffening ribs on the panel include a honeycomb core enclosed by a rigid shell formed by glass fiber reinforced resin. The entire periphery of the panel is strengthened by thickening it, and the areas to which the hinges are attached is thickened additionally.
Despite the advances which have been made in the rail car arts, such as that described in the representative patents discussed above, there continues to exist a need for further improvements in the area of covers for open top rail cars.
There continues to exist a particular need for an improved cover for an open top coal car which will act to prevent coal dust from blowing out on the trip from the coal mine to the power plant or other ultimate destination.
A need also exists for such a cover which would also act to improve fuel efficiency of the rail car as a consequence of closing the open top of the cars, thereby improving the aerodynamic characteristics of the rail car.
A need also exists for such a cover which would act to prevent the ingress of rain, snow or other precipitates into the open car interior and onto any porous material contained therein, or into an empty car.
A need exists for a universal cover which will fit all common types of rail cars, which is relatively economical to implement without requiring extensive modification of the basic rail car design.